Many methods and devices have been proposed for the preparation a frothy liquid for human consumption, such as coffee with a layer of fine-bubbled froth, cappuccino, café crème, (hot) chocolate, milk, etc.
For instance in EP 1 169 956 a coffee preparation device is disclosed wherein a buffer volume of coffee extract is received in a buffer reservoir of the device. A jet of coffee extract is jetted into this buffer volume of coffee extract, the collision causing the formation of bubbles in the coffee extract. The coffee extract flows from the buffer reservoir into a cup and a layer of froth, commonly referred to as a crema layer, is obtained on top of the coffee.
For instance in WO2005/058109 the jet of liquid is made to collide with a structural part of the device in order to cause the generation of the froth.